1. Field of the Invention
The present invention relates generally to machine tools such as turret punch presses and more particularly to a method and apparatus for controlling deformations of frames of machines to maintain a high degree of working accuracy thereof and longevity of the tools therefor.
2. Description of the Prior Art
Generally, in machine tools such as punching presses, heat will inevitably be produced because of friction and electrical resistance at various portions of the devices during operation such as bearings, clutch and brake parts and electric motors. Such heat will be produced not only over a wider temperature range and at different portions of the machine but also it will spread unevenly over the entire machine with the result that the frames of machine tools will be heated unevenly. Accordingly, some of the frames of the tools will be more deformed and some less by the heat produced during operation. This will result in the deflection of the frame out of desired conditions. Thus, in machine tools, the trouble has been that the working accuracy and the life of tools are decreased because of deformations of the frames caused by the heat produced during operation.
For instance, in a turret punch press having pairs of upper and lower punching tools, heat is liable to occur to deform the upper and lower frames in such a manner as to cause the upper and lower punching tools to deflect out of alignment with each other. Of course, when the upper and lower punching tools are not in accurate alignment with each other, the turret punch press will not be able to perform accurate punching operations and the upper and lower punching tools will also be broken or prematurely worn.
In order to overcome the above described disadvantages, some machine tools are finally assembled or completed by making adjustments after being initially warmed up by idling for hours. In this manner, however, the machine tools cannot be in the desired condition unless warmed up to the temperatures at which they were finally assembled or completed. In fact, the heat prevailing in machine tools always changes according to operation conditions. Therefore, much time is necessary, especially in winters until the machine tools are fully warmed up. Thus, it is impossible to keep the machine tools in the desired condition by finally assembling or completing the machine tools after initially warming up them. Thus, it is desirable to control the heat in the machine tools during operation.